This study considers first-degree relatives of type I diabetics to be a population at higher risk than the general population for the development of diabetes. The study aims to identify individuals within this study population at moderate to high risk for developing type I diabetes and to examine interventions to prevent diabetes. Over 700 samples have been collected from individuals in the test population. Approximately 40 demonstrated islet cell antibodies (5.3%). At the date of this report, 37 patients with islet cell antibodies have been studied on the GCRC with intravenous glucose tolerance tests and measurements of insulin autoantibodies. HLA determinations and oral glucose tolerance tests were also performed. Patients have now been randomized to the intervention limb, under which they will receive either parenteral or oral antigens (insulin or glutamic acid decarboxylase). The objective is to induce tolerance to the oral antigens, and the hypothesis is that the onset of diabetes will be delayed by this treatment. The results of this study are not yet available.